Alkylation process using hydrogen fluoride catalyst

ABSTRACT

A PROCESS FOR ALKYLATING AN ALKYLATABLE HYDROCARBON WITH AN OLEFIN-ACTING REACTANT BY CONTACTING THE ALKYLATABLE HYDROCARBON WITH A FIRST PORTION OF THE OLEFIN-ACTING REACTANT AND WITH A FIRST ALKYLATION ZONE; CONTACTING YHE HYDROCARLYST IN A FIRST ALKYLATION ZONE; CONTACTING THE HYDROCARBON EFFLUENT WITH THE FIRST ALKYLATION ZONE WITH A SECOND PORTION OF THE OLEFIN-ACTING REACTANT AND WITH A SECOND HYDROGEN FLUORIDE ALKYLATION CATALYST IN A SECOND ALKYLATION ZONE, AND RECOVERING THE ALKYLATION REACTION PRODUCT FROM THE HYDROCARBON EFFLUENT FROM THE SECOND ALKYLATION ZONE.

Aug. 20, 1974 R. F. ANDERSON ALKYLATION PROCESS USING HYDROGEN FLUORIDECATALYSI Filed sept, 21, 1972 NEQQSSQQ United States Patent O" 3,830,865ALKYLATION PROCESS USING HYDROGEN FLUORIDE CATALYST Robert F. Anderson,La Grange Park, Ill., assigner to Universal Oil Products Company, DesPlaines, lll. Continuation-impart of application Ser. No. 236,049, Mar.20, 1972. This application Sept. 21, 1972, Ser.

Int.. Cl. C07c 3/54 U.S. Cl. 260-671 R 6 Claims ABSTRACT OF THEDISCLOSURE CROSS REFERENCE TO RELATED APPLICATIONS This application is acontinuation-impart of my copending application Ser. No. 236,049, filedon Mar. 20, 1972.

BACKGROUND OF INVENTION This invention relates to a process forproducing an alkylation reaction product from an alkylatable hydrocarbonand an olefin-acting reactant. In one aspect, this invention relates toa process for alkylating an isoparaffin with an olefin-acting reactant,utilizing hydrogen fluoride catalyst, to provide valuable motor fuelcomponents. In another aspect, this invention relates to a process foralkylating an aromatic hydrocarbon with a C9-C15 olefinacting reactantutilizing hydrogen lluoride catalyst, to provide valuable alkylaromaticpetrochemical products.

Alkylation of isoparafllnic hydrocarbons, such as isobutane, isopentaneand the like, with olefinic hydrocarbons such as propylene, butylene,amylenes, and olefinacting compounds such as C3-C5 alkyl halides, etc.,using hydrogen fluoride as a catalyst, is well known as a cornmerciallyimportant method for producing gasoline boiling range hydrocarbons. TheC-Cm hydrocarbons typically produced by the isoparafn-olel'in alkylationreaction are termed alkylatef Alkylate is particularly useful as a motorfuel blending stock because of its high motor and research octaneratings, such that it can be used to improve the overall octane ratingof gasoline pools to comply with the requirements of modern automobilemtors. These high octane alkylate fuel components are particularlyimportant in producing motor fuels of sufficient quality when it isdesired not to employ alkyl lead compounds in the fuel to meet octanerequirements. A continuing goal of the art is to provide a hydrogenfluoride catalyzed alkylation process which provides an alkylate producthaving higher motor and research octane ratings than is possible usingconventional processes, in an economical manner.

In general, commercial isoparaflin-olefin alkylation processes employisobutane and sometimes isopentane as the isoparaflin and propylene,butylenes, amylenes, or a mixture thereof, as the olefin-actingreactant. The isoparaflin, olefin-acting agent and hydrogen fluoridecatallyst are contacted in an alkylation reactor, forming a reactionmixture. After the alkylation reaction is substantially complete, thereaction mixture is withdrawn from the reactor and is settled intohydrocarbon and catalyst phases 3,830,865 Patented Aug. 20, 1974 in asettling vessel, and the hydrogen fluoride catalyst thus separated isrecycled to the reactor for further use. The hydrocarbon phase producedby the settling operation is further processed by, for example,fractionation, to recover the alkylate product and to separateunconsumed isoparaflln for further use by recycle to the alkylationreactor.

It has been found necessary to conduct hydrogen lluoride-catalyzedisoparaflin-olefin alkylation processes at specific conditions oftemperature and pressure, and at specific concentrations of reactantsand catalyst in order to provide an acceptable yield of high qualityalkylate product. A large molar excess of' isoparaflin over theolefin-acting compound in the reaction mixture, generally about 10:1 toabout 30:1, is one of the conditions required to provide an adequateproduct, although low quality alkylate can be produced usingisobutane/olefin mole ratios lower than 10:1. It has been founddesirable to employ as large an excess of isoparaffln as economicallypossible, since the quality of the alkylate product is improved thereby,as exemplified by the increased octane rating of the product. Thus, inconventional operations, a considerable amount of isoparain isnecessarily recovered and recycled to the alkylation reactor afterfractionation to separate it from the alkylate fraction of thehydrocarbon phase produced by settling. The large amounts of isoparaflinwhich must accordingly be passed, unreacted, through an alkylationreactor and settler and separated from the alkylate product necessitatethe use of fractionation equipment of large capacity, with high energyconsumption, in order to provide even an adequate separation of theproduct alkylate from the isoparaflln to be recycled.

Prior art has attempted to alleviate this problem by circulating anemulsion of the hydrogen fluoride catalyst, isoparaflin, and alkylationreaction products, in an attempt to utilize the isoparaflin in thisemulsion to provide a portion of the excess isoparaflln needed. Thus,the emulsion was withdrawn from a reactor and charged into the reactoragain along with fresh olefinic reactant. Another similar prior artattempt to provide the high isoparaflin excess needed during thealkylation reaction was to pass the reaction mixture of hydrogenfluoride, isoparaflln and reaction products from a first alkylation zoneinto a second alkylation zone, where it was contacted with fresholeflnic feed and further alkylation occurred. These attempts to providea high isoparaflin/olefin mole ratio in the alklation zone failed toprovide any substantial increase in the quality of the alkylate producedand have generally been abandoned in successful commercial operations.Thus there remains significant expense and difficulty, in commercialoperations, in providing the required isoparaffin/olefin mole ratio inthe reactor, which necessitates throughput, separation and recycle ofexcessive amounts of isoparallin. This problem is substantiallyalleviated by the present invention.

Processes for the production of C9C15 side chain alkylaromatichydrocarbons using hydrogen fluoride as a catalyst have assumedsignificant importance in the petroleum and petrochemical industries foruse in providing starting materials in the manufacture of detergents.Examples of commercially important alkylaromatic alkylation processesinclude alkylation of benzene, toluene, etc., with C9-C15 linear olefinsor alkyl halides, which produce linear alkylaromatics called detergenta1- kylate. This alkylate is then further treated to producebio-degradable detergents.

Although aromatic alkylation processing conditions in hydrogen fluoridecatalyzed operations are generally more dependent on equilibriumconsiderations than are isoparaflin alkylation conditions, it has beenyfound desirable to employ a large molar excess of the alkylatablearomatie hydrocarbon over the olefin-acting reactant at aromaticalkylation conditions in order to provide adequate yields of the desiredalkylaromatic product, and also to control the temperature in thealkylation reactor. The necessity for using large excess amounts of thealkylatable aromatic hydrocarbon in the alkylation reaction leads toeconomic and technical difficulties similar to those encountered in anisoparaflin-olefin alkylation operation. For example, when benzene isalkylated with C9-C15 linear olefins, the large amount of unreactedbenzene in the alkylation reactor efiluent must be separated from theproduct through the use of large fractionation apparatus, with attendantcapital and utilities expense, and the benzene recycled to thealkylation reactor for further use. Failure to employ a molar excess ofthe alkylatable aromatic in the alkylation reaction step leads to theformation of polyalkylaromatics, polymers of the C9C15 olefinactingreactant, and other undesirable side products which are wasteful of thereactant and difficult to separate from the desired products. Theprocess of the present invention is directed, in part, to providing amethod for reducing the amount of alkylatable aromatic hydrocarbon whichmust be separated, recovered and recycled after the alkylation reaction,while the general quality and quantity of the alkylaromatic productproduced in the aromatic alkylation process is improved.

SUMMARY OF THE INVENTION It is an object of the present invention toprovide a processs for alkylating an alkylatable hydrocarbon with anolefin-acting reactant, utilizing hydrogen fluoride alkylation catalyst.

Another object of the present invention is to provide a process foralkylating an isoparafliu with an olefin-acting reactant which producesa superior alkylation reaction product.

A further object of the present invention is to provide a process foralkylating an alkylatable aromatic hydrocarbon with a C9-C15olefin-acting compound wherein an increased yield of the desiredalkylaromatic product is provided.

A further object of the present invention is to provide a process foralkylating an isoparaflin with an olefin-acting reactant wherein areduced recycle and separation of isoparaflin is utilized to provide ahigh quality motor fuel alkylate product.

A still further object of the present invention is to provide a processfor alkylating an alkylatable aromatic hydrocarbon with a C9-C15olefin-acting reactant wherein a reduced separation and recycle ofaromatic hydrocarbon is utilized to provide a desirable yield ofalkylaromatic product.

In a broad embodiment, the present invention relates to a process forproducing an alkylation reaction product from an alkylatable hydrocarbonand an olefin-acting reactant which comprises: contacting a firstportion of the olefin-acting reactant with the alkylatable hydrocarbonand with a first hydrogen fluoride alkylation catalyst in a firstalkylation zone at hydrogen fluoride alkylation conditions; removing theresultant hydrocarbons from contact with the first alkylation zone andthe first hydrogen fluoride catalyst to form a first hydrocarboneffluent stream; contacting a second portion of the olefin-actingreactant with at least a portion of the first hydrocarbon eflluentstream and with a second hydrogen fluoride alkylation catalyst in asecond alkylation zone at hydrogen fluoride alkylation conditions;removing the resultant hydrocarbons from contact with the secondalkylation zone and the second hydrogen fluoride catalyst to form asecond hydrocarbon effluent stream; and recovering the alkylationreaction product from the second hydrocarbon effluent stream.

In one limited embodiment, the present invention relates to a processfor producing an isoparaflinic alkylation reaction product fromisobutane and a C3-C5 olefin which comprises: contacting a first portionof the C3-C5 olefin with isobutane and with a first hydrogen fluoridealkylation catalyst in a first alkylation zone at hydrogen fluoridealkylation conditions; removing the resultant hydrocarbons from thefirst alkylation zone and from contact with the first hydrogen fluoridecatalyst to form a first hydrocarbon effluent stream; contacting asecond portion of the C3-C5 olefin with the first hydrocarbon effluentstream and with a second hydrogen fluoride alkylation catalyst in asecond alkylation zone at hydrogen fluoride alkylation conditions;removing the resultant hydrocarbons from the second alkylation zone andfrom contact With the second hydrogen fluoride catalyst to form a secondhydrocarbon eliiuent stream; and, recovering the isoparaflinicalkylation reaction product from the second hydrocarbon effluent stream.

In another limited embodiment, the present invention relates to aprocess for producing an alkylaromatic alkylation reaction product frombenzene and a (2Q-C15 normal olefin which comprises: contacting a firstportion of the C9-C15 normal olefin with the benzene and with a firsthydrogen fluoride alkylation catalyst in a first alkylation zone athydrogen fluoride alkylation conditions; removing the resultanthydrocarbons from the first alkylation zone and from contact with thefirst hydrogen fluoride catalyst to form a first hydrocarbon effluentstream; contacting a second portion of the C9-C15 normal olefin with thefirst hydrocarbon effluent stream and with a second hydrogen fluoridealkylation catalyst in a second alkylation zone at hydrogen fluoridealkylation conditions; removing the resultant hydrocarbons from thesecond alkylation zone and from contact with the second hydrogenfluoride catalyst to form a second hydrocarbon eflluent stream; and,recovering the alkylaromatic alkylation reaction product from the secondhydrocarbon etlluent stream.

Among the important advantages of the process of this invention overprior art processes are those which derive from a substantial reductionin the overall excess amount of the alkylatable reactant needed inrelation to the olefin. By passing only a portion of the olefin-actingreactant to the first alkylation reactor, a significantly smaller amountof the alkylatable reactant is required in the hydrogenfluoride-catalyzed alkylation reaction to provide an adequate molarexcess of alkylatable reactant in relation to the amount ofolefin-acting reactant utilized. The hydrocarbon etlluent from the firstreactor and settled is then contacted with a second portion of theolefin-acting compound in a second hydrogen fluoride catalyzedalkylation reaction, whereby the same relatively small amount ofalkylatable reactant is utilized to provide the desired molar excess ofalkylatable reactant in both the first and the second reactors, athydrogen fluoride alkylation conditions. The hydrocarbon eflluent fromthe second reactor is then treated, e.g. by conventional fractionation,to separate and recycle the excess alkylatable reactant and to recoverthe desired alkylation reaction product. The amount of excessalkylatable reactant which must be thus separated and recycled issubstantially less than that found in conventional alkylation processes.Alternatively, a conventional amount of recycled alkylatable reactantmay be employed, giving a superior reaction product.

I have found that the benefits of providing a high molar excess ofisoparflin in an alkylation reactor cannot be achieved when theisoparaflin is used in the form of an emulsion or mixture with thehydrogen fluoride catalyst. Instead, it is necessary to first separatethe isoparafiin from the catalyst. When the isoparafiin is used as anemulsion, there is little or no benefit in respect to alkylate quality.By using the method of the present invention, whereby the isoparafiin isfirst separated from the first hydrogen fluoride catalyst and thensubsequently utilized in the second alkylation zone with a differenthydrogen fluoride catalyst, this isoparaflin acts, substantially, like afresh isoparaffin feed. Conversely, the prior art method in which theisoparafiin is employed in admixture with hydrogen DESCRIPTION OF THEDRAWING The attached drawing is a schematic illustration of a preferredembodiment of the process of the present invention. In the particularembodiment set forth, the alkylatable hydrocarbon is isobutane and theolefin-acting reactant is a mixture of propylene and butylenes. Thescope of the present invention is not intended to be limited to theembodiment shown, and various other suitable reactants and embodimentswill be obvious to those skilled in the art from the descriptionhereinafter provided.

Referring to the drawing, a conventional olefin feed to a hydrogenuoride catalyzed isoparafn-olefin alkylation process is chargedcontinuously through conduit 1. The olens are chaged at a rate of about300 moles/hour propylene and 300 moles per hour butylenes. In addition,smaller amounts of other hydrocarbons which are conventionally presentin a commercial olefin feedstock, but not necessary for operation of theprocess, including 120 moles/hour isobutane, 35 moles/hour n-butane and70 moles/hour propane, are charged through conduit 1 in admixture withthe olefins. The continuously charged hydrocarbons in conduit 1 aredivided into two streams of equal volume and passed into conduits 2 and3. The olefinic feedstocks passed into conduits 2 and 3 thus bothcomprise 150 moles/ hour propylene, 150 moles/ hour butylenes, 60moles/hour isobutane, 17.5 moles/ hour n-butane and 35 moles/hourpropane. Make-up isobutane is charged via conduit 4 into conduit 2 andadmixed in conduit 2 with the portion of the olefin feedstock therein.The make-up isobutane stream is passed through conduit 4 at a rate of500 moles/hour of isobutane, with conventional amounts of non-reactivecontaminants including about 15 moles/hour n-butane and about 10moles/hour propane. The admixed make-up isobutane and olefin feedcontinues through conduit 2, and recycled isobutane from conduit 26 ispassed into conduit 2 and admixed with the contents thereof. The recycleisobutane is passed into conduit 2 at the rate of 3550 moles/ hourisobutane, with some other non-reactive hydrocarbon recycle, resultingfrom imprecise fractionation, including 525 moles/hour n-butane and 225moles/ hour propane. The total hydrocarbon charge to reactor 5 thusincludes 150 moles/hour propylene, 150 moles/hour butylenes, 411()moles/hour isobutane, with non-reactive hydrocarbons including 270moles/hour propane and 557.5 moles/hour n-butane. The isobutane/olefinmole ratio of the feed to reactor S is thus 13.7. The combined feed ispassed through conduit 2 into reactor 5 and admixed with hydrogenfluoride alkylation catalyst to form a reaction mixture. The hydrogenfluoride alkylation catalyst is charged to reactor 5 through conduit 12.The catalyst contains about 80 wt. percent acid, less than about 1 wt.percent Water, with the remainder being conventional organic diluent.Alkylation conditions maintained in reactor 5 include a temperature ofabout 90- 100 F. and a pressure suicient to maintain the reactants andcatalyst in the liquid phase. An acid/hydrocarbon volume ratio of about1 to about 2 is also maintained. Heat generated in the alkylationreaction is withdrawn through the use of indirect heat exchange. Coolingwater is charged through conduit 6 into reactor 5, and passed inindirect heat exchange with the reaction mixture. Used cooling water iswithdrawn via conduit 7. After a contact time of about 0.1 minute toabout 5 minutes, the reaction mixture in reactor 5 is withdrawn andpassed through conduit 8 into reaction soaker 9. The reaction mixture ofcatalyst, reactants and reaction products is maintained 6 in reactionsoaker 9 for about 1 minute to about 10 minutes at a temperature andpressure about the same as employed in reactor 5. The reaction mixtureis then withdrawn and passed through conduit '10 into settler l11. Thereaction mixture is allowed to stand without agitation in settler 11,whereby the hydrogen fluoride catalyst forms a heavier phase and thehydrocarbon components of the reaction mixture form a lighter phase. Thelower, catalyst phase is withdrawn from the bottom of settler 11 throughconduit 12 and passed back to reactor 5 for further catalytic use. Itmay be necessary to treat a portion of the recycle catalyst to maintainthe desired acid strength, etc. This can be done by passing a slipstream of catalyst from conduit 12 to conventional regeneration means.Such a regeneration operation being conventional not essential to anunderstanding of the present invention, the mode of performance thereofwill be obvious to those skilled in the art, and the operation is notincluded in the drawing and description thereof. Referring again tosettler 11, the hydrocarbon phase formed therein, which includes thetotal hydrocarbon eiuent from reactor 5 and reaction soaker 9, iswithdrawn from the top of settler 11 via conduit 13, and passed intoconduit 3 wherein the total hydrocarbon efuent from the tirst alkylationzone (which includes reactor 5, reaction soaker 9 and settler 1-1) iscommingled with the portion of olefin feed in conduit 3. The hydrocarboneiuent passed through conduit 13 includes approximately 3800 moles/hourisobutane, substantially no olens, 557.5 moles/hour n-butane, 280moles/hour propane and 300 moles/hour of alkylate. The combinedhydrocarbon charge to reactor 14 from conduit 3 includes about 3860moles/hour isobutane, 150 moles/hour propylene, 150 moles/hourbutylenes, 57:5 moles/hour n-butane, 315 moles/hour propane and 300moles/hour alkylate. The isobutane/olefin mole ratio of the hydrocarboncharge to reactor 14 is thus about 13. The reaction conditions employedin reactor 14 are similar to those employed in reactor S, i.e., atemperature of about 90100 F., acid/hydrocarbon Volume ratio of about 1to about 2 and a pressure sufficient to maintain the reaction mixturecomponents in the liquid phase. Hydrogen uoride catalyst containingabout wt. percent acid, less than about 1 wt. percent water, with theremainder made up of organic diluent, is charged to reactor 14 throughconduit 21 and intimately admixed with the hydrocarbon feed from conduit3 to form the reaction mixture. Cooling Water is charged through conduit15 and passed in indirect heat exchange with the reaction mixture inreactor 14. Used cooling Water is withdrawn through conduit 116. After acontact time of about 0.1 minute to about 5 minutes, the reactionmixture is withdrawn from relactor 14 and passed through conduit 17 intoreaction soaker 18. The reaction mixture of catalyst, reactants andreaction products is maintained in reaction soaker 18 for a contact timeof about 1 minute to about 10 minutes at a temperature and pressuresubstantially the same as employed in reactor -14. The reaction mixtureis then withdrawn and passed through conduit 19 into settler 20. Thereaction mixture is allowed to stand without agitation in settler 20 tofacilitate separation of the catalyst and hydrocarbons into separatephases. The heavier, catalyst phase is withdrawn from the bottom ofsettler 20 through conduit 21 and recycled to reactor 14 for furthercatalytic use as described. A portion of the catalyst in conduit 21 maybe passed to a conventional regeneration operation if desired. Theupper, hydrocarbon phase in settler 20 is Withdrawn through conduit 22and continuously passed into isobutane stripper 23. The hydrocarboneffluent from settler 20 is passed through conduit 22 at the rate ofabout 325 moles/hour propane, 3550 moles/hour isobutane, 575 moles/hourn-butane and -600 moles/hour alkylate (C5+ hydrocarbons). In isobutanestripper 23, the hydrocarbon effluent from settler 20 is fractionated toseparate a recycle isobutane stream and a product alkylate stream. Thevessel employed as the isobutane stripper contains conventional trays,reboiling means, relluxing means, etc., all known in the art. Alkylateproduct is removed as a bottoms product from isobutane stripper 23through conduit 24, passed out of the operation, and recovered for motorfuel or other desired uses at the rate of 600 moles/hour. Normal butane,by-product of the process in the embodiment shown, is withdrawn as aside cut through conduit 25 at the rate of 50 moles/hour. Recycleisobutane is withdrawn as a side cut on a higher tray in isobutanestripper 23 through conduit 26. The recycle isobutane stream is passedout of isobutane stripper 23 through conduit 26 at the rate of 3320moles/hour isobutane, 500 moles/hour n-butane and 225 moles/hourpropane. The recycle isobutane stream in conduit 26 is passed intoconduit 2 as described above. An overhead stream is withdrawn fromisobutane stripper 23 and passed through conduit 27 into depropanizer28. The overhead stream is passed from the isostripper at the rate of100 moles/hour propane, 230 moles/hour isobutane and 25 moles/hourn-butane. In depropanizer 28, the feed from conduit 27 is fractionatedto separate propane from isobutane and n-butane. The isobutane andn-butane are withdrawn, at the rate of 230 moles/hour isobutane and 25moles/hour n-butane, as a bottoms product and passed through conduit 29into conduit 26 for use in the recycle isobutane stream. Propane,admixed with some hydrogen fluoride, is withdrawn overhead throughconduit 30, at the rate of 100 moles/hour propylene, and passed throughconduit 30 into conduit 31 in admixture with hydrogen fluoride fromconduit 38. The mixture of propane and hydrogen fluoride in conduit 31is passed into condenser 32 and condensed to liquefy the propane andacid. The liquefied propane and hydrogen lluoride are then passedthrough conduit 33 into settler 34. Most of the hydrogen fluoride passedinto settler 34 settles out las a heavy phase of relatively pure acidand is withdrawn through conduit 35. This relatively concentrated acidmay be passed back into the recycle catalyst streams in conduit 12 andconduit 21, by conventional means not shown. The liquefied propane phasein settler 34 is withdrawn and passed through conduit 36 into hydrogenfluoride stripper 37, wherein the propane is fractionated to separateout any remaining acid. The acid is withdrawn overhead through conduit38, passed back into conduit 31, and treated as described above. Thepropane is withdrawn as a by-product from the bottom of hydrogenfluoride stripper 37 through conduit 39 at the rate of 100 moles/hour.Certain conventional equipment and operations necessary for theoperation of the embodiment described in the foregoing have been omittedfrom the dawing and description thereof, e.g. pumps, valves, reboilers,etc. The use and placement of such conventional items will be obvious tothose skilled in the art. The foregoing description illustrates some ofthe advantages of the present invention when embodied in a hydrogenfluoride-catalyzed isoparailin-oleiin alkylation process. For example,reaction conditions in reactor and reactor 14 include a desirable highisobutane/olefin mole ratio of about 13: 1, necessary in order toproduce alkylate of suflicient quality. Yet fractionation requirementsin isobutane stripper 23 need only be sufficient to separate isobutaneequivalent to an overall isobutane/olefin mole ratio of less than 7:1.The alkylate produced is of a quality equal or superior to alkylateproduced in conventional alkylation processes, while the fractionationrequirements are substantially reduced, with the attendant savings incapital and utilities costs. By contrast, alkylate produced in aconventional hydrogen fluoride catalyzed alkylation process using anoverall isobutane/olefin mole ratio of 7:1 would be low in quality andlack utility as a blending stock to upgrade low gasoline pool componentsto the desired octane level.

8 DETAILED DESCRIPTION OF INVENTION The hydrogen fluoride catalyzedalkylation process of the present invention may be applied to thealkylation of isoparatiins, alkylatable aromatics or other suitablealkylatable hydrocarbons such as naphthenes, etc. In a preferredembodiment wherein an isoparain is employed as the alkylatablehydrocarbon, the preferred isoparallins are isobutane and isopentane,particularly isobutane. A mixture of two or more isoparaflins may alsobe employed, if desired. A suitable isoparain feedstock for use in thepresent process may contain some .non-reactive contaminants such asnormal parans. For example, a conventional commercial isobutanealkylation feedstock generally contains about 95 wt. percent isobutane,4 wt. percent n-butane and l wt. percent propane.

Oleiin-acting reactants suitable for use in the process of the presentinvention, in a preferred embodiment Wherein the alkylatable hydrocarbonis an isoparaflln, include CZ-C olelins and alkyl lluorides. Ca-Colefins and alkyl fluorides are preferred, particularly propylene,butylenes and amylenes. It is to be understood that mixtures of two ormore olefin-acting compounds may be employed in the present process withgood results. For example many conventional olefin feedstocks incommercial isoparainolefin alkylation operations contain mixtures ofpropylene and butylenes, butylenes and amylenes, or propylene, butyleneand amylenes. The benefits of the present process can be obtained usingsuch feedstocks as well as when using single olefin-acting compounds.Similarly, a mixture of C3-C5 alkyl lluorides and oletins in anyproportion is also suitable. The particularly preferred C3-C5 olefinfeedstocks may be derived from petroleum refining processes such ascatalytic cracking and may contain substantial amounts of saturates,lighter and heavier olens, etc.

The hydrogen fluoride catalyst employed in the present process, inembodiments wherein the alkylatable hydrocarbon is isobutane, is wellknown in the art. Generally, this hydrogen fluoride alkylation catalystcontains about 75 wt. percent or more of titratable acid, about 5 wt.percent or less water, with the remainder being organic diluent. Such analkylation catalyst is suitable for use in both the first and secondalkylation reactors in the present process. A particularly preferredcatalyst contains about wt. percent acid, less than l wt. percent water,the remainder being organic diluent.

Numerous alkylation reaction zones suitable for use in the process ofthis invention are known in the art. For example, but not by way oflimitation, the alkylation reactor described in U.S. Pats. 3,456,033,3,469,949 and 3,501,536 may suitably be employed for both alkylationreactions when alkylating an isoparain with an olefin using the hydrogenfluoride catalyst. Alkylation conditions associated with the particularalkylation reactors described in the above-listed patents or inconnection with other suitable conventional alkylation reactors may beused in conjunction with the description herein in embodiments of thepresent invention. Particular alkylation zones and optimum alkylationconditions in specific embodiments of the present process depend uponthe composition of the particular olefin-acting reactant, the particularalkylatable hydrocarbon, and the strength of the hydrogen fluoridecatalysts.

Hydrogen fluoride alkylation conditions suitable for use in anembodiment of the present process in which the alkylatable hydrocarbonis an isoparatiin include a temperature of about 0 F. to about 200 F., apressure suicient to maintain the reactants and the hydrogen fluoridecatalyst in the liquid phase, and a contact time between thehydrocarbons and catalyst of about 0.1 minute to about 30 minutes. In apreferred embodiment utilizing a hydrogen fluoride alkylation catalystcontaining about 75-85 wt. percent acid, a catalyst/hydrocarbon volumeratio of about 0.1 to about 10 is preferred, and a temperature of about50 F. to about 150 F. is preferably employed in the reactor.

In a particularly preferred embodiment, the reaction mixture of hydrogenuoride catalyst, reactants and reaction products formed in thealkylation reactor is passed through a reaction soaker. In thedescription of the preferred embodiments herein provided, it is intendedthat both the alkylation reactor and a reaction soaker, if one isutilized, are included within the scope of the term alkylation zone.Suitable reaction soakers are well known in the art. For example, thereaction soakers described in U.S. Pats. 3,560,587 and 3,607,970 maysuitably be employed in the present process. Such reaction soakers arecommonly vessels equipped with perforated trays,

baflle sections, or the like, to maintain the mixture of catalyst andhydrocarbons charged from the alkylation reactor as a fairly homogeneousmixture, or emulsion, for a predetermined length of time. The mixture ofcatalyst and hydrocarbons is maintained in the reaction soaker for atime which depends on the composition of the reaction mixture. Areaction soaker residence time of about 1 minute to about 30 minutes ispreferred. The temperature and pressure maintained in the reactionsoaker are the same as the temperature and pressure maintained in thealkylation reactor.

Means for separating a hydrocarbon phase and a hydrogen fluoridecatalyst phase out of the reaction mixture effluent from an alkylationreactor or reaction soaker, to provide the hydrocarbon eflluent from thealkylation zone, are well known in the alkylation art. Generally, theeflluent from an alkylation reactor or soaker comprises a mixture ofisoparailln, reaction products, hydrogen fluoride catalyst andcatalyst-soluble organic materials, possibly with small amounts of lighthydrocarbon gases, etc. When this mixture is allowed to stand unstirred,i.e., settled, the reaction products, isoparaffin and light hydrocarbongases form a hydrocarbon phase containing a small amount of catalyst insolution. The catalyst and catalyst-soluble hydrocarbons form a separatephase. The hydrocarbon phase is then easily mechanically separated fromthe catalyst phase. The term hydrocarbon eflluent stream is intended toinclude this hydrocarbon phase, when removed from a settler. Thetemperature and pressure maintained during such a settling operation ina hydrogen fluoride catalyzed alkylation process are substantially thesame as those described above in connection with hydrogen fluoridealkylation conditions employed in a reactor. The hydrocarbons and thecatalyst are preferably maintained in the liquid phase during theseparation operation.

Some means for withdrawing heat from the alkylation zone is necessaryfor operation of the process. A variety of means for accomplishing theheat withdrawal are Well known. For example, in one embodiment the heatgenerrated in the alkylation reaction may be withdrawn directly from thealkylation reactor by indirect heat exchange between cooling water andthe reaction mixture in the reactor.

The hydrocarbon effluent stream, recovered from the first alkylationzone by settling the reaction mixture to separate the hydrocarbonefiluent from the hydrogen fluoride catalyst, is preferably combinedwith a second portion of the olefin-acting reactant and then charged tothe second alkylation reactor, wherein this combined hydrocarbons streamis contacted with a second hydrogen fluoride alkylation catalyst. It iscontemplated that sufllcient isoparaflin is charged to the first reactorso that no further isoparafn need be added to the hydrocarbons chargedto the second reactor. Generally, the total isoparain charge to thealkylation process through, in turn, the first alkylation zone and thenthe second alkylation zone. Under some conditions, it may beadvantageous to charge some further fresh isoparaflin to the secondalkylation reactor, and such a modification is within the scope of thisinvention. The hydrocarbons recovered from the second reaction andseparation procedure may be passed to conventional fraction operationsand equipment, such as an isobutane stripper, whereby the alkylateproduct is separated from unconsumed isoparafln and any hydrogenfluoride which may be present in the hydrocarbon effluent from thesecond alkylation zone. Any suitable method utilized in the prior art tofractionate the hydrocarbon eflluent from a settler may be employed toseparate the alkylate product from the isoparaflln and possibly hydrogenfluoride.

The alkylation reaction product produced in the preferred embodiment ofthe present process, when an isoparafln is employed as the alkylatablereactant, will generally comprise C7 and heavier saturated hydrocarbonsresulting from the alkylation reactions of the isoparaflin with theolefin-acting reactant in both the first and second alkylation zones.The primary products include, for example, dimethylpentanes andtrimethylpentanes. It is well known that more highly branchedhydrocarbons possess superior properties as motor fuel, and the presentinvention is directed, in part, to providing motor fuel alkylatecontaining a higher ratio of more highly branched hydrocarbons, such astrimethylpentanes, to less branched hydrocarbons, such asdimethylhexanes. This benet is obtained by the use in the presentprocess of high isoparaflln/ olefin mole ratios, unattainable in priorart process on any economical or operative basis. Thus, it is apparentthat the present invention provides a novel process for producing asuperior motor fuel alkylate product by a method more economical andconvenient than has been available in prior art hydrogenfluoride-catalyzed alkylation processes.

When the alkylatable hydrocarbon employed in the process of the presentinvention is an alkylatable aromatic, the preferred alkylatablehydrocarbons are monocyclic aromatics such as benzene, toluene, xylenes,ethylbenzene, cumene, trimethylbenzenes, diand triethylbenzene, etc.,particularly benzene. The present process is applicable to a wide rangeof alkylatable aromatics but will be described in terms of a mono-cyclicaromatic such as benzene for the sake of brevity. Those skilled in theart will recognize the broader aspects of the present invention from thedescription provided.

The olefin-acting reactants which may suitably be employed inembodiments of the present process wherein the alkylatable hydrocarbonis an aromatic include nonenes, decenes, undecenes, dodecenes,tridecenes, tetradecenes, pentadecenes, and mixtures thereof. C9-C15alkyl halides may also be utilized with good results. Particularlypreferred are the C9-C15 normal mono-olefins and normal alkyl iluorides.These suitable olefin-acting reactants may be utilized when admixed withsome nonreactive contaminants such as Cg-Cls parafflns, etc.

The catalyst employed in the process of the present invention toalkylate an alkylatable aromatic with a suitable olefin-acting reactantis hydrogen fluoride containing about wt. percent or more of titratableacid. Hydrogen fluoride alkylation conditions employed in thisembodiment include a temperature of about 0 F. to about 200 F. andsufficient pressure to maintain the reactants in the liquid phase. Ingeneral, the conditions and procedure are very similar to those employedin using the hydrogen fluoride catalyst as described in the embodimentwherein an isoparaflin was the alkylatable hydrocarbon. The hydrogenfluoride catalyst, benzene and a first portion of a C9-C15 olefin arecontacted in the first alkylation reactor to form a reaction mixture.The mixture is then settled to separate the hydrocarbons from thecatalyst, and the catalyst is recycled to the reactor for further use.The hydrocarbon effluent from the first alkylation zone is then passedto the second alkylation reactor and contacted with a second portion ofthe (iQ-C15 n-olefin and a second hydrogen fluoride catalyst to form asecond reaction mixture. The second reaction mixture is settled and thecatalyst is recycled to the second reactor. The hydrocarbon effluentfrom the second alkylation zone is then fractionated to separate andrecover the linear alkylbenzene product and the unreacted benzene. Theproduct is removed, and the benzene is recycled to the first alkylationzone for further use. A benzene/ olefin mole raito of about :1 or moreis preferred in such an operation to provide an adequate yield of theproduct and prevent formation of olefin polymers and polyalkylbenzene.

In general, the benefits and advantages of the present process areprovided when the alkylatable hydrocarbon is contacted with at least twodifferent portions of the olefinacting reactant and two differenthydrogen fluoride catalysts in at least two different alkylation zones.One obvious modification of the present process is to divide theolefinacting reactant into a plurality of portions, e.g. three or more.The alkylatable reactant and a first portion of the olefin-actingreactant are contacted with hydrogen fluoride in a first alkylationzone, the catalyst and hydrocarbons are separated, and the hydrocarboneflluent from the first alkylation zone and a second portion of theolefin-acting reactant are contacted with hydrogen fluoride in a secondalkylation zone, and the catalyst-free hydrocarbon effluent from thesecond alkylation zone and a third portion of the o1efin-acting reactantare contacted with hydrogen fluoride in a third alkylation zone, etc.The catalyst-free hydrocarbon eflluent from the last alkylation zone inthe series is fractionated to recover the alkylation reaction productand separate the remaining alkylatable reactant for recycle to the firstalkylation zone. Such a scheme is Within the scope of the presentinvention.

Where it is desired to employ two alkylation zones and to divide theolefin-acting .reactant into two portions7 as in the preferredembodiment described, it is preferred that the portions be such thatneither portion contains less than about 10 volume percent of the totalamount of olefin-acting reactant used in the process. For example, in-

a continuous operation, the first portion of olefin-acting reactant maybe fed to the first alkylation zone at a rate of 10 moles/hour alongwith an amount of alkylatable hydrocarbon sufficient to provide thedesired molar excess thereof in the first reactor at hydrogen fluoridealkylation conditions. The second portion of olefin-acting reactant is,in this case, preferably fed into the second alkylation zone at a rateof at least about 1 mole/ hour and not more than about 100 moles/ hour.Preferably the two portions of olefin-acting compound do not vary in theamount of olefin-acting compound they contain by more than about 1:5 toabout 5:1, by volume. Best results are achieved in a two-reactor system,as described in the preferred embodiments, when the two portions ofolefin-acting reactant contain roughly equal amounts of theolefin-acting reactant. In this way, the amount of alkylatablehydrocarbon needed to provide an optimum molar excess in each alkylationzone at hydrogen fluoride alkylation conditions is kept to a minimum,while the highest quality product possible can thereby be obtained fromboth the first and second reactors.

I claim as my invention:

1. A process for producing an alkylation reaction product from analkylatable aromatic hydrocarbon and an olefin-acting reactant whichcomprises the steps of:

(a) contacting a first portion of said olefin-acting reactant with saidaromatic hydrocarbon and with a first hydrogen fluoride alkylationcatalyst in a first alkylation zone at hydrogen fluoride alkylationconditions;

(b) removing the resultant mixture of hydrocarbons and catalyst fromsaid first alkylation zone, separating the hydrocarbons from said firsthydrogen fluoride catalyst to form a first hydrocarbon eflluent streamand recycling thus separated catalyst to said first zone;

(c) contacting a second portion of said olefin-acting reactant with atleast a portion of said first hydrocarbon eflluent stream and with asecond hydrogen fluoride alkylation catalyst in a second alkylation zoneat hydrogen fluoride alkylation conditions;

(d) removing the resultant hydrocarbons and catalyst from said secondalkylation zone and separating the hydrocarbons from said secondhydrogen fluoride catalyst to form a second hydrocarbon effluent stream,recycling thus separated second catalyst to said second zone, andrecovering said alkylation reaction product from said second hydrocarboneffluent stream.

2. The process of Claim 1 wherein said first portion of saidolefin-acting reactant comprises about 10 vol. percent to about 1,000No1. percent of said second portion of said olefin-acting reactant.

3. The process of Claim 1 wherein said alkylatable aromatic hydrocarbonis a monocyclic aromatic selected from benzene, toluene, ethylbenzeneand cumene.

4. The process of Claim 1 wherein at least a portion of said secondhydrocarbon effluent stream is fractionated to form said alkylationreaction product and an aromatic hydrocarbon recycle stream and at leasta portion of said recycle stream is introduced into said firstalkylation zone.

5. The process of Claim 3 wherein said olefin-acting compound isselected from nonenes, decenes, undecenes, dodecenes, tridecenes,tetradecenes and pentadecenes.

6. The process of Claim 3 wherein said olefin-acting compound is aC9-C15 alkyl halide.

References Cited UNITED STATES PATENTS 3,007,983 11/1961 ClausOIl260-683.46 3,236,912 2/1966 Phillips 260-683.49 2,818,452 12/1957 Mavity260-671 P 3,207,800 9/1965 WilliamsOn et al. 260-671 B 2,395,775 2/1946AndersOn 260-671 P 3,422,161 1/1969 Lavigne et al 260--671 B 3,433,8463/1969 Adams et al 260-671l B 3,483,265 12/1969 Rakestraw et al. 260-671B 3,494,971 2/1970 Penske 260-671 B CURTIS R. DAVIS, Primary ExaminerU.S. C1. X.R. 260-671 B, 671 P

